I have to admit I'm a little baffled by Van's procedure to align the gear leg fairings. The plane is in the air now and I would like to get it done before I drop it onto the gear. If I cut the slots in the top of the fairing where the clamp attaches will I be able to adjust the fairing by turning it if it proves to be misaligned? I have "eyeballed" the fairing to leg fit and am convinced that even though Van says not to do this I can get it real close to where the centerline of the fairing is centered on the gear leg in a manner to cause the least amount of drag. I would like to fit the fairing and clamp to the leg now by eyeball and when finally flying if the leg is misaligned as indicated by the ball in my turn coordinator fine tune it than. Does this sound feasible or will the clamp prevent the turning of the leg? Or am I way off and should start all over again using Van's method which is giving my brain pain.
Van's Air Force
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gear leg fairing alignment question
- Thread starter JimWoo50
- Start date
gmcjetpilot
Well Known Member
Good idea but....
The eye ball is great but you are talking about fairings that are swept aft and tapered. Kind of hard to eye ball, but may be your eye ball is better calibrated than mine. Nothing wrong with eye ball, but measuring it is not as hard as you think. I recommend you try Van's method or one of several variations people have adapted as a double check.
How to check: Its hard to put into words and there has been several RVator articles and many builder sites (with pictures) that show clever and efficient ways to align. The basic string method works OK. Wrap the string around the gear leg and run the ends aft to a central point. that is parallel to the ground (aircraft in level flight attitude) and parallel to the center line of the fuselage. There are two challenges, one is getting that point to pull the string, and two is making the small measurements between the string and trailing edge.
To get center line I take some plumb-bob drops and drawing a center line on the hanger floor. Than I cut a large piece of wood, old door works good because its flat and stiff. It has a center line and is cut to fit under plane. You can shoot or transfer the projection of the gear leg (leg not faring) onto the wood and note stations along or down the gear leg you'll check at. The wood template is perpendicular to the floor and center line on floor.
When done marking the wood template, you move it to the back of the plane and line it up with center line on the floor and make perpendicular again center line and floor. (The floor has to be flat of course) Than you just need to pull the string which is wrapped around the fairing to the wood template.
One modification is to run the string though a light plastic ring you can slide along the string. The idea is slide the ring up forward to the gear leg so you can see the difference in trailing edge to string easier. As you slide the ring forward it pulls the string together closer to the trailing edge. Hope I did not confused you. Here is a thumb nail pic I made, click it once or twice.
See individual notes above. I agree 100% with the logic but your idea the slip ball will be fine enough to make gear leg fairing adjustments is probably not going to work. You could use dirty or colored oil and go fly. You check to see how the oil runs aft on the top and bottom surfaces.JimWoo50 said:
The eye ball is great but you are talking about fairings that are swept aft and tapered. Kind of hard to eye ball, but may be your eye ball is better calibrated than mine. Nothing wrong with eye ball, but measuring it is not as hard as you think. I recommend you try Van's method or one of several variations people have adapted as a double check.
How to check: Its hard to put into words and there has been several RVator articles and many builder sites (with pictures) that show clever and efficient ways to align. The basic string method works OK. Wrap the string around the gear leg and run the ends aft to a central point. that is parallel to the ground (aircraft in level flight attitude) and parallel to the center line of the fuselage. There are two challenges, one is getting that point to pull the string, and two is making the small measurements between the string and trailing edge.
To get center line I take some plumb-bob drops and drawing a center line on the hanger floor. Than I cut a large piece of wood, old door works good because its flat and stiff. It has a center line and is cut to fit under plane. You can shoot or transfer the projection of the gear leg (leg not faring) onto the wood and note stations along or down the gear leg you'll check at. The wood template is perpendicular to the floor and center line on floor.
When done marking the wood template, you move it to the back of the plane and line it up with center line on the floor and make perpendicular again center line and floor. (The floor has to be flat of course) Than you just need to pull the string which is wrapped around the fairing to the wood template.
One modification is to run the string though a light plastic ring you can slide along the string. The idea is slide the ring up forward to the gear leg so you can see the difference in trailing edge to string easier. As you slide the ring forward it pulls the string together closer to the trailing edge. Hope I did not confused you. Here is a thumb nail pic I made, click it once or twice.
Last edited:
JordanGrant
Well Known Member
Jim,
The gear leg fairing alignment was a challenge for me. I had another post on this sometime in the recent past, but here is another explanation of my experience:
1) I originally "aligned" my fairings by just lining them up with Bob Snedaker's upper gear leg fairings. I supplemented using the Mark-1 Eyeball method, and they looked straight. However, my RV-6 came out with a very significant yaw when flying with the fairings on - so back to the drawing board.
2) I re-fit the fairings using the Van's string method, which was very confusing to me as well, at first. George's drawing should hopefully clear it up somewhat. That got me closer, but unfortunately did not take out all of the yaw. I still had nearly a full ball-width out of trim at cruise speeds. Back to the drawing board.
3) Third time, I used the trial-and-error method. I had a good place to start from using the string method, so I went from there. I had taken off the lower and upper fairings, so that meant I could adjust the leg fairings in small amounts to test the impact on flying qualities. I just marked where they were on the gear leg, then adjusted from there. Clamping down the hose clamp really tight kept them very securely in place. Then I just went flying and saw how it did. I was careful to be relatively consistent with my data points - same altitude and airspeed for each run. I found that I could take out the yaw, but the adjustment created some "heavy wing" when I did it. Makes sense, of course.
4) Another method I tried was to go flying with the hose clamps on a bit loose. I would fly the airplane up to redline airspeed (180kts, RV-6) and keep it straight with appropriate rudder. The idea was to have the fairings streamline to the relative wind, and see where they came out. This worked out OK - not perfectly. They gave me another datapoint for placing the fairings.
5) In the end, I found a happy medium, close to where the fairings streamlined, but not perfectly. They work a bit as a trim tab for yaw, but they give me a little bit of rolling moment as well. I wouldn't say I'm thrilled with the outcome, but they are functional.
YMMV,
The gear leg fairing alignment was a challenge for me. I had another post on this sometime in the recent past, but here is another explanation of my experience:
1) I originally "aligned" my fairings by just lining them up with Bob Snedaker's upper gear leg fairings. I supplemented using the Mark-1 Eyeball method, and they looked straight. However, my RV-6 came out with a very significant yaw when flying with the fairings on - so back to the drawing board.
2) I re-fit the fairings using the Van's string method, which was very confusing to me as well, at first. George's drawing should hopefully clear it up somewhat. That got me closer, but unfortunately did not take out all of the yaw. I still had nearly a full ball-width out of trim at cruise speeds. Back to the drawing board.
3) Third time, I used the trial-and-error method. I had a good place to start from using the string method, so I went from there. I had taken off the lower and upper fairings, so that meant I could adjust the leg fairings in small amounts to test the impact on flying qualities. I just marked where they were on the gear leg, then adjusted from there. Clamping down the hose clamp really tight kept them very securely in place. Then I just went flying and saw how it did. I was careful to be relatively consistent with my data points - same altitude and airspeed for each run. I found that I could take out the yaw, but the adjustment created some "heavy wing" when I did it. Makes sense, of course.
4) Another method I tried was to go flying with the hose clamps on a bit loose. I would fly the airplane up to redline airspeed (180kts, RV-6) and keep it straight with appropriate rudder. The idea was to have the fairings streamline to the relative wind, and see where they came out. This worked out OK - not perfectly. They gave me another datapoint for placing the fairings.
5) In the end, I found a happy medium, close to where the fairings streamlined, but not perfectly. They work a bit as a trim tab for yaw, but they give me a little bit of rolling moment as well. I wouldn't say I'm thrilled with the outcome, but they are functional.
YMMV,
gmcjetpilot
Well Known Member
One more thought
I like Jordan Grant method.
Here is one idea. FLY WITH OUT GEAR LEG or WHEEL FAIRING, and get the plane to fly straight with out any gear or wheel fairings. Once the plane is in rig you can add the fairing and do flight test to determine affect. However you can get into where different parts are fighting each other.
The down side is taking the plane off of flight to spend time to add fairings.
I like Jordan Grant method.
Here is one idea. FLY WITH OUT GEAR LEG or WHEEL FAIRING, and get the plane to fly straight with out any gear or wheel fairings. Once the plane is in rig you can add the fairing and do flight test to determine affect. However you can get into where different parts are fighting each other.
The down side is taking the plane off of flight to spend time to add fairings.
I will make first flights without fairings
and use your idea to get the aircraft in rig without the fairings and work from there. It seems to be very commonsensical. I will be using a newly overhauled engine and have read the best break in procedure is to run it hard and this is easier to do without going too fast ( I hope to have this problem) without the fairings installed. Thanks again.
and use your idea to get the aircraft in rig without the fairings and work from there. It seems to be very commonsensical. I will be using a newly overhauled engine and have read the best break in procedure is to run it hard and this is easier to do without going too fast ( I hope to have this problem) without the fairings installed. Thanks again.
